低温氦气体轴承透平膨胀机实验系统设计

设计了一套氦透平膨胀机实验系统,该系统可以用来对工作在液氢—常温区范围内的不同规格的氦透平膨胀机进行性能测试,还可以用于开展以氦为工质的低温环境下透平膨胀机实验研究,以期掌握氦透平膨胀机的关键技术并进一步提高氦透平膨胀机的性能。     

回热循环燃气轮机中回热器的动态特性研究

采用多段集中参数模型对具有分布参数特性的回热器建模，简化了由偏微分方程带来的大量计算，应用Matlab／Simlink软件作为仿真平台，采取数值方法求解，对具体回热燃气轮机中的回热器进行了仿真，结果表明，回热器时间常数较大，在回热循环燃气轮机仿真中回热器的热惯性不能忽略，而且是影响系统平衡稳定性的重要因素．     

Optimization of helium refrigerators and liquefiers for large superconducting systems

A general method for optimizing ideal Claude cycles with multiple expansion engines is presented for two types of engine arrangements. In one case, the inlet temperature of one engine is equal to the outlet temperature of another engine. In the second case, inlet and outlet temperatures of adjacent engines are independent of each other, the more general case which is sometimes used in practice. The optimizing technique is especially adapted to superconductive systems in which some of the helium vapour is used to cool electrical leads and mechanical support systems. The helium fraction to be returned to the refrigerator-liquefier vs the fraction to be used for other purposes is conventionally entered as a parameter which becomes part of the optimization technique.     

Experimental and simulation-based analysis of asymmetrical spherical roller bearings as main bearings for wind turbines

Symmetrical spherical roller bearings (SSRB) used as main bearings for wind turbines are known for their high load carrying capacity. Nevertheless, even designed after state-of-the-art guidelines premature failures of this bearing type occur. One promising solution to overcome this problem are asymmetrical spherical roller bearings (ASRB). Using ASRB the contact angles of the two bearing rows can be adjusted individually to the load situation occurring during operation. In this study the differences between symmetrical and asymmetrical spherical roller bearings are analyzed using the finite element method (FEM). Therefore, FEM models for a three point suspension system of a wind turbine including both bearings types are developed. These FEM models are validated with measurement data gained at a full-size wind turbine system test bench. Taking into account the design loads of the investigated wind turbine it is shown that the use of an ASRB leads to a more uniform load distribution on the individual bearing rows. Considering fatigue-induced damage an increase of the bearing life by 62% can be achieved. Regarding interactions with other components of the rotor suspension system it can be stated that the transfer of axial forces into the gearbox is decreased significantly.

     

Corrosion in coal-fired gas turbines

The purpose of this paper is to review corrosion processes and experience related to coal-fired gas turbines. For over 40 years there have been major programmes of research directed towards burning coal in a gas turbine either directly or as a coal-derived fuel. This history is briefly reviewed, demonstrating the importance which corrosion of the hot section has had in limiting the achievements and defining the systems. The probable corrosion mechanisms are identified, and because of their synergistic interaction with corrosion, erosion and deposition are also considered. The discussion identifies pressurized fluidized bed combustion (PFBC) as the direct combustion technique most likely to be able to avoid serious corrosion problems in the immediate future. Recent results from PFBC pilot plant investigations related to turbine materials are compared, and thereby future directions for overcoming corrosion problems are proposed. MST/449     

Experience with platinum aluminide coatings in land-based gas turbines

Hot-corrosion crucible tests with salt mixtures which simulated actual blade deposits were carried out to evaluate the potential of platinum-modified aluminide coatings for application in advanced industrial gas turbines. In comparison with simple aluminide coatings, a significantly improved resistance against hot corrosion at intermediate temperatures was found. At the highest turbine-operating temperature, coating life exceeds that of conventional plasma-sprayed NiCrSi coatings. Actual engine test results are presented which confirm the beneficial role of platinum. However, the susceptibility of platinum aluminide coatings to crack formation and propagation may make them unsuitable for application to rotating blades.     

Methodology for the systematic design of conical plain bearings for use as main bearings in wind turbines

With the possibility to replace sliding segments on the tower without disassembling the drivetrain, the use of segmented plain bearings with conical sliding surfaces as main bearing in wind turbines has a great potential to reduce the maintenance costs and thus the levelized cost of energy (LCOE). Furthermore, the short axial design leads to lower investment costs. Since this design is totally new and no design guidelines are available so far, the objective of this paper is to investigate the influence of the geometric parameters on the hydrodynamic pressure distribution of the bearing. In this context a parameter screening is performed using a suitable test field according to Plackett and Burman in order to determine the most relevant parameters. With the help of the simulations carried out after this test field, correlations between the geometric parameters and the hydrodynamic pressure distribution are evaluated. To be able to quantitatively analyze the three-dimensional pressure distribution, several key values are defined in this paper that describe the pressure distribution. The content of this paper is part of a methodology with the goal of developing a design guideline for conical plain bearings.

     

A dynamic simulation of the conforming shell gas journal bearing

A time-dependent mathematical model for the conforming shell gas journal bearing is presented. A numerical scheme is devised to solve this mathematical model. The results of a dynamic simulation of the bearing are exhibited for a specific design.     

An efficient cryopump for exchange gas in dilution refrigerators

A simple cryopump is described, which efficiently removes the exchange gas from the inner vacuum space of a dilution refrigerator.     

Hot corrosion site environment in gas turbines

The importance and complexity of environmental influences on the hot corrosion process in gas turbines is now recognized. The present paper seeks to emphasize that the hot corrosion phenomenon is the end product of a chain of events which starts at the air / sea interface (encompassing wind speed, relative humidity, intake siting, etc) and which extends through filter performance, compressor operating characteristics, and flame tube design before terminating at the hot corrosion site, i.e. the high-pressure rotors. Attention is particularly drawn to the influence exerted by both salt and carbon particulate material and their interrelationship with each engine stage upstream of the turbine.     

Concurrent product and closed-loop supply chain design with an application to refrigerators

Increased concern for the environment has lead to new techniques to design products and supply chains that are both economically and ecologically feasible. A literature study shows that many models exist to support product design and logistics separately. In our research, we develop quantitative modelling to support decision-making concerning both the design structure of a product, i.e. modularity, reparability and recyclability, and the design structure of the logistic network. Environmental impacts are measured by linear-energy and waste functions. Economic costs are modelled as linear functions of volumes with a fixed set-up component for facilities. This model is applied to a closed-loop supply chain design problem for refrigerators using real life R&D data of a Japanese consumer electronics company concerning its European operations. The model is run for different scenarios using different parameter settings such as centralized versus decentralized processing, alternative product designs, varying return quality and quantity, and potential environmental legislation based on producer responsibility.     

Lifing methods and safety criteria in aero gas turbines

Modern gas turbines engines concentrate high power into a relatively small machine, e.g. more than 50 MW in each engine suspended from the aircraft wing in a large civil transport application. The rotational speed of the shafts reaches as high as 13,000 rpm in large engines and even higher in smaller engines as used in helicopters. Hence there is both a concentration of thermal energy in the combustion process and kinetic energy in the rotating parts that presents issues for structural integrity. This paper describes the regulatory requirements that must be achieved to allow operation of engines in civil applications and at how these requirements are satisfied in practice. It concentrates on those parts whose failure can directly threaten the integrity of the airframe through the generation of hazardous effects. The main issues are associated with fatigue through cyclic operation of the engine and the ability of the engine to survive abnormal conditions in such a way that the aircraft can safely land and be brought to rest.     

Lifing issues in hot gas path components of heavy-duty gas turbines

Abstract

Gas turbine hot-gas-path components, which include combustion liners, transition pieces, turbine nozzles and turbine buckets, are exposed to hot gases discharged from combustion systems and suffer from severe materials degradation and damage even in the early stage of operation. The severity of the damage and degradation increases with increasing inlet temperature and size of the gas turbines, which also increase the maintenance cost. ‘Lifing’ of components is, therefore, becoming a very critical issue. This paper describes several kinds of component damage and material degradation occurring in the 1,100°C- and 1,300°C-class heavy-duty gas turbines and then shows how we revised those component lives from the original design ones. Analytical-based assessment methods associated with condition-based assessment ones, some examples of assessment results, and component life extension technologies are also described.     

Coatings in industrial gas turbines: Experience and further requirements

In-service experience with and results of laboratory tests of coatings for industrial gas turbine applications are discussed. The examples considered include corrosion-protective coatings for severe corrosive environments, erosion- corrosion-protective coatings, wear-protective coatings and thermal barrier coatings. The chemical, mechanical and other physical properties required for the coatings are summarized. The applications of advanced or new technologies are discussed briefly with respect to low grade fuels, advanced process parameters and new materials.     

相似理论在高温气冷堆氦气压气机中的应用

根据相似理论推导出在不同工质条件下进行压气机模化试验的决定性相似准则数并加以敏感性分析,研究发现马赫数小于0．5时,绝热指数对模拟性能试验引起的偏差很小;在几何相似的基础上,只需使流量系数φ和压头系数ψ相等就能保证运动相似,从而保证模型与原型流动相似。研究发现氦气轮机部分工况下的低雷诺数会降低压气机气动性能和稳定性。在确定了压气机模化试验参数的基础上,由氦气压气机设计工况推导出使用空气进行模拟试验时压气机的特性曲线图,为氦气压气机的试验与优化设计提供了理论依据。     

Protecting bearings and extending their service life

The move towards more integrated bearing structures means that the importance of seals and shields is growing. Such components, which are often termed ‘add-on items’, are fast becoming part of the bearings that they are designed to protect.     

混合轴承多跨转子多频轴承传递力自适应控制

介绍了一种基于电磁执行器动力特性可控的混合轴承结构;用有限元法建立了多跨转子系统的动力学模型,分析了转子通过轴承给基础的传递力及传递力控制的原理;基于自适应最小均方算法,提出了一种基于误差信号子带滤波,由多个单频力控制器并联而成的变步长自适应轴承传递力控制器;以双轴多跨转子系统为例对轴承传递力主动控制器的有效性进行了理...     

Analysis of DC gas flow in GM type double inlet pulse tube refrigerators

In a GM type double inlet pulse tube refrigerator, a DC gas flow is an intrinsic phenomenon. It is important to understand the characteristics of the DC gas flow. In this paper, the relation between the DC gas flow, valve operating time intervals, and flow patterns in the bypass of the GM type double inlet pulse tube refrigerator is studied with a numerical simulation when a symmetric bypass is used. The governing equations of the numerical simulation based on the nodal analysis are discretized with an implicit finite volume method. The simulation result shows that the valve opening angle difference is the main parameter having influence on the DC gas flow, and the effect depends on the flow patterns in the bypass.